1. Field of the Invention
Embodiments of the present invention relate generally to novel polymer compositions which are useful in the manufacture of medical implants. More particularly, embodiments of the present invention relate to blended polymer compositions having an additive ingredient, which produces a blend having a lower tensile strength when compared to the polymer composition without the additive ingredient. The blended polymer compositions are biodegradable or bioresorbable. Methods of lowering the tensile strength of a copolymer are also disclosed. The novel polymer compositions can be fashioned into medical implants for implantation in the body.
2. Description of Related Art
Biodegradable polymer materials and blends thereof used for the production of implants, and implants themselves, are known. See for example U.S. Pat. Nos. 5,700,901; 5,502,159; 5,868,746; 5,569,250; 6,093,201; 5,314,989; 5,403,347; 5,372,598; 4,905,680; 5,468,242; and 5,690,631 each of which are hereby incorporated by reference in their entireties for all purposes. However, blends of polymers with copolymers which result in reduced tensile strength of the implant fashioned therefrom and resulting cold-bendable properties have not been disclosed.
Embodiments of the present invention relate generally to novel polymer compositions which are useful in the manufacture of medical implants. The polymer compositions are biocompatible and bioresorbable. According to one embodiment of the present invention, a lactic acid or glycolic acid based polymer or copolymer is blended with one or more copolymer additives. The resulting blend is used to form an implant, for example, by well known methods such as melt blending and injection molding and the like. The resulting implant exhibits a lower tensile strength and a higher ductility when compared to an implant formed from a polymer or copolymer lacking the one or more copolymer additives. A copolymer additive according to the present invention includes a bioresorbable monomer and a monomer capable of lowering the tensile strength of the overall polymer composition. As a result, implants fashioned from the novel polymer compositions of the present invention exhibit advantageous properties of being cold-bendable, i.e. bendable at room temperature without crazing or cracking. In addition, the implants of the present invention are capable of being rejuvenated, i.e. cold-bendable properties which may be reduced over long periods of time can be restored by warming the implant.
Embodiments of the present invention also include methods of making implants and the resulting implants themselves which exhibit reduced tensile strength due to the incorporation of the copolymer additive into a bioresorbable polymer or copolymer either before or during the extrusion process. According to the method, a bioresorbable polymer or copolymer is provided. The bioresorbable polymer or copolymer can be mixed with the copolymer additive and then the mixture melt-blended. Alternatively, the individual components can be melted separately or sequentially and then blended together prior to an injection molding process.
Embodiments of the present invention are still further directed to methods of recovering initial physical properties of implants formed from the polymer compositions of the present invention. According to the present invention, physical properties of implants formed from the present invention are allowed to change through, for example, the passage of time as can be associated with shelf life. The implant is then heated, for example, on a temperature controlled heating plate for a time period sufficient to restore approximately the initial physical properties of the implant.
Accordingly, it is an object of the present invention to provide polymer compositions having reduced tensile strength and increased ductility. It is another object of the present invention to provide polymer compositions useful in the production of biodegradable or bioresorbable implants. It is yet another object of the present invention to provide a method of altering the tensile strength of implants to accommodate a particular implant use. It is still yet another object of the present invention to provide a biodegradable or bioresorbable implant which is cold bendable, i.e. bendable at room temperature without crazing or cracking. It is a further object of the invention to eliminate the need for the preheating of implants prior to implantation into the body. It is a yet further object of the present invention to provide a method of restoring approximately the initial physical properties of the implant. These and other objects, features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings.